1. Field of the Invention
This invention relates generally to telephone devices. More particularly, it relates to a home networking communication system for networking computers within a small environment such as a home.
2. Background of Related Art
There has been an explosive growth in the use of telephone lines in many households, driven largely by the need for simultaneous Internet access, voice communications, networking, etc. Many households and small business are already wired with a telephone line, providing the basis for a convenient wired network.
The HomePhoneline Networking Alliance (HomePNA) is an association of leading companies working together to help ensure adoption of a single, unified phoneline networking industry standard and rapidly bringing to market a range of interoperable home networking solutions. With homenetworking, households receive the benefits of simultaneous, shared internet access, printer/peripheral sharing, file and application sharing, and networked gaming. In addition, consumers can enjoy the use of each of these home entertainment and information services using existing wiring in the home.
Home PNA 2.0 offers several advantages over older technologies. Like the first-generation PNA, it uses your existing phone lines, but it can operate at speeds up to 32 Mbps. Unlike Ethernet, Home PNA doesn't require a hub; each PC simply connects to the nearest telephone jack, but doesn't interfere with the phone's normal operation.
A home networking system is a communication system used to link home personal computers and home electronic appliances together. The media of the link may be, e.g., telephone line, power line or wireless media. The protocol may be, e.g., Ethernet or other LAN (local area network).
An exemplary home networking system 600 is illustrated in FIG. 9 linking, e.g., a first PC 602, a washer 604, a dryer 606, a second PC 608, a stove 610, a video 612, and an audio device 614.
Currently, as many as five (or more) services may co-exist on a single copper pair (i.e., telephone line). They are voice band service (POTS), ISDN service, ADSL service, HPNA (Home Phone line Network Alliance) service and VDSL service. HPNA exists within a home on an internal copper pair, the other services are delivered to the home on an external copper pair.
FIG. 10 shows a conventional distribution of spectral regions typically used for various services, e.g., voice services, xDSL services such as ADSL and g.Lite or G.922.2, and of a home network such as HPNA.
As shown in FIG. 10, a single telephone line is shared such that the various services co-exist as a type of FDM (Frequency Division Multiplex) system. In this arrangement, Plain Old Telephone Service (POTS) exists in the 0-4 kHz region, an exemplary xDSL service may be present from 25 kHz to approximately 2.2 MHz (depending on the definition of “x”), and the HPNA spectrum occupies 5.5-9.5 MHz for HPNA V1.x technology or 4.25-9.75 MHz for the emerging V2.x technology.
FIG. 11 depicts the HPNA description of a conventional HPNA compliant transmitter which generates a physical layer (PHY) signal.
In particular, as shown in FIG. 11, an HPNA transmitter 800 consists of a frame processor 802, a data scrambler 804, a bit-to-symbol mapper (i.e., constellation encoder) 806, and a QAM (e.g., FDQAM) modulator 808.
The output of the HPNA transmitter 800 is a 4 MBaud quadrature amplitude modulation (QAM) and 2 MBaud Frequency Diverse QAM (FDQAM), with 2 to 8 bits-per-Baud constellation encoding, resulting in a physical layer payload modulation rate that ranges from 4 Mb/s to 32 Mb/s. Information is transmitted on the HPNA channel in bursts, or frames.
FIG. 12 shows the HPNA2.x standard frame 900, which is based on telephone line and Ethernet protocol.
In particular, FIG. 12 shows exemplary conventional Home PNA network packet frames 900a, 900b, including a training sequence (TRN) 902a, 902b, a head portion (HEAD) 904a, 904b, and a data payload (DATA) 906a, 906b. 
The training sequence (TRN) 902 is a predefined preamble (e.g., 64 symbols) in each Home PNA network packet frame 900. The header (HEAD) 904 includes information relating to the source and destination addresses, and the Ethernet type. The data payload (DATA) 906 includes the Ethernet compliant data payload and error checking information.
The Home PNA network packet frames 900 are basic information cells transferring data from one Home network station to another. An Inter Frame Gap (IFG) 920 is between each Home PNA network packet frame 900. The IFG 920 relates to the silence (no signal) time between two adjacent Home PNA network packet frames 900.
FIG. 13 shows in more detail the physical layer (PHY) HPNA packet frame format.
In particular, as shown in FIG. 13, each conventional HPNA physical layer frame 900 consists of variable-rate payload information 906 encapsulated by a low-rate header 904 including preamble information 11, and a low-rate trailer 1006. While in the HPNA 2.0 standard the preamble information 11 is defined as being included in the header 904, it is shown separately in FIG. 13 for ease of description herein.
The conventional Home PNA network packet frame format includes an Ethernet compatible sub-frame 930. This allows Home PNA networking systems to be 100% compatible with current Ethernet devices. Moreover, the use of an Ethernet sub-frame 930 allows the use of existing Ethernet protocol chip sets without the need for redesign.
The preamble PREAMBLE64 11 forms a training period which allows a receiver to train appropriate components, e.g., an equalizer, timing recovery, automatic gain control (AGC), an echo canceler, etc. The PREAMBLE64 11 is defined as a repetition of four 16 symbol sequences (TRN16) that result from encoding at 2 Mbaud, 2 bits-per-Baud, with the scrambler 804 (FIG. 11) disabled. The TRN16 is a constant amplitude QPSK sequence, designed to facilitate power estimation and gain control, baud frequency offset estimation, equalizer training, carrier sense, and collision detection.
The header 904 includes frame control information 12, and the initial portion of an otherwise standard Ethernet packet 930. In particular, the header 904 further includes a destination address (DA) 13, a source address (SA) 14, and an Ethernet type 15.
The frame control field 12 of the header 904 is defined as a 32-bit field as shown in FIG. 14. The frame control field 12 consists of, in the following order, a frame type (FT), scrambler initialization bits (SI), priority (PRI), a reserved field (RSVD), payload encoding information (PE), and a header check sequence (HCS). Also in the header 904, the destination address (DA) 13 and the source address (SA) 14 are each 24 symbol values, in accordance with Ethernet standards.
The data payload 906 includes the end portion of the otherwise standard Ethernet packet 930, in particular the Ethernet data 20, a Frame Check Sequence (FCS) 21, a 16-bit cyclic redundancy check (CRC) 21, a pad field (PAD) 22 consisting of a number of octets inserted, and an end-of-frame (EOF) sequence delimiter 23 consisting of the first 4 symbols of the TRN sequence from the preamble 11.
Using this conventional approach to Home networking, a predefined preamble 11 of, e.g., 64 symbols, is required before each Ethernet frame to allow synchronization and reliable reception. For instance, the 64 symbols provide time for the receiver to train appropriate components such as an equalizer, timing recovery, an automatic gain controller (AGC), and an echo canceler. However, because the Home PNA 2.0 is a packetized data standard, the receiver must re-train its components for reception of each Home PNA packet network frame 900. While this is a reasonable approach, it is appreciated by the present inventors to have certain disadvantages.
For instance, the training of the equalizer, timing recovery circuits, AGC, echo canceler, etc. during reception of the preamble is commonly referred to as “blind training”, meaning that the receiver station doesn't know any information about the incoming signal before it trains its components during reception of the preamble. Thus, the equalizer must be re-trained from scratch for reception of each Home PNA packet network frame 900. The same for the timing recovery circuits, the AGC, and any echo canceler. Thus, blind training has to accommodate different communication channels and/or different Ethernet types, which significantly impacts performance and/or cost.
While the Home PNA 2.0 standard provides a given amount of time, e.g., 64 symbols worth of time, this time is considered by the present inventors to be short, causing ‘quickened’ training of the appropriate receiver circuits such as the equalizer, timing recovery, AGC, echo canceler, etc., resulting in limited receiver performance.
Another disadvantage is that in HPNA, the Ethernet type includes different baud rates in the DATA period. For each different baud rate, the optimal equalizer training is completely different. So, in the case of blind training, either multiple equalizers must be used, with each equalizer optimally matching each baud rate (increasing cost), or a single equalizer must be implemented which compromises over the different baud rates ultimately reducing performance.
Yet another disadvantage is that in the Ethernet protocol, two adjacent frames may be completely independent, meaning that the two frames may be transmitted from different stations. Thus, their channel properties may be completely different. In this case, the blind training cannot make use of any pre-determined information or any channel information, thus also limiting performance.
There is a need for a technique in home networking communication that permits frame training in a high performance and cost effective manner.